US11021649B2 - Flowback resistant proppants - Google Patents
Flowback resistant proppants Download PDFInfo
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- US11021649B2 US11021649B2 US15/919,399 US201815919399A US11021649B2 US 11021649 B2 US11021649 B2 US 11021649B2 US 201815919399 A US201815919399 A US 201815919399A US 11021649 B2 US11021649 B2 US 11021649B2
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- United States
- Prior art keywords
- proppant
- resin coated
- curable resin
- coated proppant
- addition copolymer
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- 229920005989 resin Polymers 0.000 claims abstract description 137
- 239000011347 resin Substances 0.000 claims abstract description 137
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- 238000000576 coating method Methods 0.000 claims description 62
- 239000002245 particle Substances 0.000 claims description 43
- 239000011248 coating agent Substances 0.000 claims description 42
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 14
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 11
- 125000000217 alkyl group Chemical group 0.000 claims description 7
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- 238000004132 cross linking Methods 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 5
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 5
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- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
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- 239000000839 emulsion Substances 0.000 claims description 3
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 claims description 2
- IMROMDMJAWUWLK-UHFFFAOYSA-N Ethenol Chemical compound OC=C IMROMDMJAWUWLK-UHFFFAOYSA-N 0.000 claims description 2
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 2
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 claims description 2
- XYLMUPLGERFSHI-UHFFFAOYSA-N alpha-Methylstyrene Chemical compound CC(=C)C1=CC=CC=C1 XYLMUPLGERFSHI-UHFFFAOYSA-N 0.000 claims description 2
- 239000001530 fumaric acid Substances 0.000 claims description 2
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 claims description 2
- 239000011976 maleic acid Substances 0.000 claims description 2
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 claims description 2
- HJWLCRVIBGQPNF-UHFFFAOYSA-N prop-2-enylbenzene Chemical compound C=CCC1=CC=CC=C1 HJWLCRVIBGQPNF-UHFFFAOYSA-N 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 54
- 239000004576 sand Substances 0.000 description 43
- 239000002952 polymeric resin Substances 0.000 description 29
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- 229920000642 polymer Polymers 0.000 description 23
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- 238000012360 testing method Methods 0.000 description 21
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- 238000000034 method Methods 0.000 description 12
- 229920003986 novolac Polymers 0.000 description 11
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 8
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- 238000006731 degradation reaction Methods 0.000 description 4
- 238000010981 drying operation Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 230000002028 premature Effects 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 238000013459 approach Methods 0.000 description 3
- 238000001723 curing Methods 0.000 description 3
- 150000002148 esters Chemical class 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
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- 239000003973 paint Substances 0.000 description 3
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 2
- 239000005995 Aluminium silicate Substances 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000012190 activator Substances 0.000 description 2
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- 235000012211 aluminium silicate Nutrition 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
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- 239000000378 calcium silicate Substances 0.000 description 2
- 229910052918 calcium silicate Inorganic materials 0.000 description 2
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 239000003431 cross linking reagent Substances 0.000 description 2
- 230000000593 degrading effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
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- 238000000638 solvent extraction Methods 0.000 description 2
- 239000000454 talc Substances 0.000 description 2
- 229910052623 talc Inorganic materials 0.000 description 2
- 229920002803 thermoplastic polyurethane Polymers 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 229920005789 ACRONAL® acrylic binder Polymers 0.000 description 1
- 244000144725 Amygdalus communis Species 0.000 description 1
- 235000011437 Amygdalus communis Nutrition 0.000 description 1
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- 244000205479 Bertholletia excelsa Species 0.000 description 1
- 235000012284 Bertholletia excelsa Nutrition 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 241000167854 Bourreria succulenta Species 0.000 description 1
- 244000068645 Carya illinoensis Species 0.000 description 1
- 235000009025 Carya illinoensis Nutrition 0.000 description 1
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- 235000013162 Cocos nucifera Nutrition 0.000 description 1
- 244000303965 Cyamopsis psoralioides Species 0.000 description 1
- BRLQWZUYTZBJKN-UHFFFAOYSA-N Epichlorohydrin Chemical compound ClCC1CO1 BRLQWZUYTZBJKN-UHFFFAOYSA-N 0.000 description 1
- 240000007049 Juglans regia Species 0.000 description 1
- 235000009496 Juglans regia Nutrition 0.000 description 1
- 239000005909 Kieselgur Substances 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- 229920000168 Microcrystalline cellulose Polymers 0.000 description 1
- 240000007817 Olea europaea Species 0.000 description 1
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- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
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- 238000013019 agitation Methods 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 235000020224 almond Nutrition 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
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- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
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- 235000005822 corn Nutrition 0.000 description 1
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- 229920001971 elastomer Polymers 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
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- 230000000149 penetrating effect Effects 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- XHXFXVLFKHQFAL-UHFFFAOYSA-N phosphoryl trichloride Chemical compound ClP(Cl)(Cl)=O XHXFXVLFKHQFAL-UHFFFAOYSA-N 0.000 description 1
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- 239000005060 rubber Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- UGTZMIPZNRIWHX-UHFFFAOYSA-K sodium trimetaphosphate Chemical compound [Na+].[Na+].[Na+].[O-]P1(=O)OP([O-])(=O)OP([O-])(=O)O1 UGTZMIPZNRIWHX-UHFFFAOYSA-K 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/68—Compositions based on water or polar solvents containing organic compounds
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
- C09K8/805—Coated proppants
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/86—Compositions based on water or polar solvents containing organic compounds
- C09K8/88—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
Definitions
- resin coated proppants Two types of resin coated proppants are used in the hydraulic fracturing of oil and gas-bearing subterranean formations—those in which the resin is uncured or only partially cured, which are known as “curable resin coated proppants,” and those in which the resin is essentially fully cured, which are known as “tempered” or “pre-cured” resin coated proppants.
- curable resin coated proppants those in which the resin is essentially fully cured, which are known as “tempered” or “pre-cured” resin coated proppants.
- the purpose and effect of the resin coating is to increase the strength of the “proppant pack” (amalgamated proppant mass) formed by the proppant downhole in the sense of resisting degradation due to the elevated temperatures and pressures encountered there.
- Curable resin coated proppants differ from tempered resin coated proppants in that their curable resin coatings cure in response to the elevated temperatures encountered downhole. This causes the resin coatings of the individual proppant particles to bond one another, thereby forming a polymer network which tends to capture and hold the individual proppant particles forming the proppant pack in place.
- curable resin coated proppants are normally used when the subterranean formation to be fractured is prone to proppant flowback.
- Proppant flowback is the problem that occurs when individual proppant particles released from a degrading proppant pack flow back into the well.
- Curable resin coated proppants tend to alleviate this problem, because the polymer network formed by the curable resin coatings of this type of proppant tends to capture and hold the individual proppant particles in place, even after proppant pack degradation, thereby preventing them from flowing back into the well.
- tempered resin coated proppants are normally used, because the enhanced ability of curable resin coated proppants to capture and hold individual proppant particles released from a degrading proppant pack is not needed in these applications.
- both types of resin coated proppants i.e., both curable and tempered
- the curable polymer resin is a novolac
- these products are normally made by melt coating the proppant substrate particle, which is normally sand, with a preformed novolac.
- the curable polymer resin is a phenolic or epoxy urethane
- these products are normally made by an in situ polymerization coating technique in which a low molecular weight phenolic or epoxy resin and an isocyanate-functional hardener are combined with the sand in such a way that the phenolic or epoxy urethane resin is formed at the same time it coats the sand.
- the polymer resin system is heated to relatively high temperature, e.g., 300° F. ( ⁇ 149° C.) or more, which is usually done by heating the sand before it is combined with the polymer system.
- relatively high temperature e.g. 300° F. ( ⁇ 149° C.) or more
- high intensity mixing such as accomplished with a Roberts Sinto or Barber Greene type pug mill is normally required. Because of these requirements, it is conventional practice in industry to carry out resin coating in a separate manufacturing plant, i.e., in a plant which is separate from the sand plant in which the raw sand is cleaned and classified into useful commercial grade sand products. This, of course, adds considerable time and expense to the cost of manufacturing these products.
- the inventive resin coated proppant is far easier and less expensive to make and use than a conventional curable resin coated proppant, because no initiator is needed to effect proppant particle bonding, because less polymer resin is needed to make the proppant, and because the high temperature/high intensity mixing coating techniques needed to make conventional curable resin coated proppants are unnecessary.
- this invention provides a resin coated proppant comprising a proppant substrate particle and coating of a polymer resin on the proppant substrate particle or an optional intermediate coating layer carried by the proppant substrate particle, wherein the polymer resin is a self-bonding addition copolymer of a vinyl aromatic comonomer and an acrylic comonomer comprising an alkyl ester of acrylic acid, methacrylic acid or both and one or more alkyl groups contain 1 to 12 carbon atoms, and further wherein the resin coating has been made by forming a mixture of a mass of the proppant substrate particles and an aqueous dispersion of the self-bonding addition copolymer and drying the mixture so formed without heating to above 300° F.
- the polymer resin is a self-bonding addition copolymer of a vinyl aromatic comonomer and an acrylic comonomer comprising an alkyl ester of acrylic acid, methacrylic acid or both and one or more alkyl groups contain 1 to 12 carbon atoms
- this invention also provides a process for producing a resin coated proppant comprising forming a mixture of proppant substrate particles and an aqueous dispersion of a self-bonding addition copolymer of a vinyl aromatic comonomer and an acrylic comonomer comprising an ester of acrylic acid, methacrylic acid or both and one or more alkyl groups contain 1 to 12 carbon atoms and drying the mixture so formed without heating to above 300° F. ( ⁇ 149° C.).
- this invention also provides a process for the hydraulic fracturing of a subterranean formation penetrated by a well comprising pumping a hydraulic fracturing fluid containing a mass of proppants down the well at a pressure high enough to fracture the subterranean formation, wherein the mass of proppants comprises the above resin coated proppant.
- FIG. 1 is a graph showing the results obtained in the following Example 9.
- the inventive curable resin coated proppant comprises a proppant substrate particle carrying a coating of a self-bonding addition copolymer of a vinyl aromatic comonomer and an acrylic ester comonomer.
- any particulate solid which has previously been used or may be used in the future as a proppant in connection with the recovery of oil, natural gas and/or natural gas liquids from geological formations can be used as the proppant substrate particle of the inventive self-suspending proppants.
- These materials can have densities as low as ⁇ 1.2 g/cc and as high as ⁇ 5 g/cc and even higher, although the densities of the vast majority will range between ⁇ 1.8 g/cc and ⁇ 5 g/cc, such as for example ⁇ 2.3 to ⁇ 3.5 g/cc, ⁇ 3.6 to ⁇ 4.6 g/cc, and ⁇ 4.7 g/cc and more.
- graded sand, bauxite, ceramic materials, glass materials, polymeric materials, resinous materials, rubber materials, nutshells that have been chipped, ground, pulverized or crushed to a suitable size e.g., walnut, pecan, coconut, almond, ivory nut, brazil nut, and the like
- seed shells or fruit pits that have been chipped, ground, pulverized or crushed to a suitable size (e.g., plum, olive, peach, cherry, apricot, etc.)
- chipped, ground, pulverized or crushed materials from other plants such as corn cobs, composites formed from a binder and a filler material such as solid glass, glass microspheres, fly ash, silica, alumina, fumed carbon, carbon black, graphite, mica, boron, zirconia, talc, kaolin, titanium dioxide, calcium silicate, and the like, as well as combinations of these different materials.
- intermediate density ceramics densities ⁇ 3.1-3.5 g/cc
- normal frac sand density ⁇ 2.65 g/cc
- bauxite high density ceramics
- Resin coated varieties of these particulate solids can also be used.
- the polymer system which is used to make the inventive curable resin coated proppants is an aqueous dispersion of a self-bonding vinyl aromatic/acrylic ester addition copolymer. More specifically, this polymer system is an aqueous dispersion of a self-bonding addition copolymer of a vinyl aromatic comonomer and an acrylic alkyl ester comonomer comprising an alkyl ester of acrylic acid, methacrylic acid or both in which the alkyl groups contain 1 to 12 carbon atoms.
- the self-bonding addition copolymer of this invention can be made from any vinyl aromatic comonomer including mixtures of different vinyl aromatic comonomers. Normally, it will be made from styrene, ⁇ -methyl styrene, vinyl toluene or mixtures thereof.
- this self-bonding addition copolymer can be made from any alkyl ester of acrylic acid, methacrylic acid or both in which the alkyl groups contain 1-12 alkyl carbon atoms. Mixtures of these alkyl groups also be used to form these esters. Esters made with methyl, ethyl and 2-ethylhexyl alkyl groups are especially interesting.
- the relative amounts of the vinyl aromatic comonomer and acrylic ester comonomer in this self-bonding addition copolymer can vary widely, and essentially any amount can be used. Normally, the amounts of each of these comonomers will be at least 10 wt. %, based on the total weight of the addition copolymer. More typically, the amounts of each of these comonomers will be at least 15 wt. %, at least 20 wt. %, at least 25 wt. %, at least 30 wt. %, at least 35 wt. %, or even at least 40 wt. % on this basis.
- addition comonomers can also be included in these self-bonding addition copolymers, examples of which include vinyl chloride, vinyl alcohol, vinyl acetate, various dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, etc. If so, the total amount of these other addition comonomers should be 40 wt. % or less, based on the weight of the self-bonding addition copolymer. Normally, the total amount of these other addition comonomers will be 30 wt. % or less, 20 wt. % or less, 10 wt. % or less, 5 wt. % or less, or even 2 wt. % or less.
- the addition copolymers used to make the inventive resin coated proppants are self-bonding.
- self-bonding means that, when the carrier liquid of the aqueous dispersion supplying this addition copolymer evaporates, the individual particles of addition copolymer in this dispersion coalesce and bond to one another to form a coherent coating—much in the same way that drying of a conventional house paint causes a smooth continuous paint coating to form.
- these self-bonding addition copolymers will bond solely under the influence moderate temperatures as low as 70° F. ( ⁇ 21° C.) and lower, with additional curing means such as the application of UV radiation, using additional curing agents, etc., being unnecessary.
- additional curing means such as the application of UV radiation, using additional curing agents, etc.
- self-bonding addition copolymers that are capable of self-bonding at temperatures as low as 70° F. ( ⁇ 21° C.) or even less will normally be used for carrying out this invention
- self-bonding addition copolymers which are capable of self-bonding at higher minimum temperatures, e.g., as low as 80° F. ( ⁇ 27° C.), as low as 90° F. ( ⁇ 32° C.), as low as 100° F. ( ⁇ 38° C.) and even as low as 120° F. ( ⁇ 49° C.) can also be used.
- Aqueous dispersions of self-bonding vinyl aromatic/acrylic ester addition copolymers which can be used to made the inventive curable resin coated proppants are widely available commercially, and essentially any such commercial aqueous dispersion can be used.
- examples include the Acronal line of self-crosslinking acrylic dispersions available from BASF, the RHOPLEX and PRIMAL lines of self-crosslinking acrylic emulsions available from Dow Chemical Company, the Vinnapas line of self-crosslinking acrylic dispersions available from Wacker Chemicals, and similar lines of self-crosslinking acrylic dispersions available from other vendors such as Bayer, Arkema and Henkel.
- an aqueous dispersion of the above self-bonding addition copolymer is combined with a mass of proppant substrate particles and the mixture so formed allowed to dry. Some additional mixing and/or heating of this mixture can occur to promote uniform coating, although this is not absolutely necessary.
- this coating and drying operation is accomplished without heating the mixture of proppant substrate particles and polymer coating resin to a temperature above 300° F. ( ⁇ 149° C.). This is not to say that this coating and drying operation must not be accomplished above this temperature—only that heating to above this temperature is unnecessary and therefore can be avoided, if desired. More typically, this coating and drying operation will be accomplished without heating the mixture of proppant substrate particles and polymer coating resin to a temperature above 250° F. ( ⁇ 121° C.), above 225° F. ( ⁇ 107° C.), above 200° F. ( ⁇ 93° C.), above 175° F. ( ⁇ 79° C.) or even above 150° F. ( ⁇ 66° C.).
- this coating and drying operation is also preferably accomplished without subjecting the mixture of proppant substrate particles and polymer coating resin to high intensity mixing, although gentle mixing can be used if desired.
- “high intensity” mixing will be understood to mean the type of vigorous mixing that occurs when conventional resin coated proppants are made in mixing equipment (e.g., pug mills) appropriate for this purpose such as available from Roberts Sinto, Barber Greene and many others.
- this type of mixing equipment is designed for applications in which large amounts of particulates such as sand, other proppants, gravel, limestone and the like are mixed and coated with relatively small amounts of liquids such as asphalt, molten novolac resins, phenolic urethane resins and the like. Because the amount of liquid coating is relatively small compared to the amount of particulate being coated, and further because relatively large amounts of particulates are processed, high energy intense mixing is normally required to insure that the particulates are coated uniformly.
- curable resin coated proppants are normally made by procedures which require heating the mixture of proppant substrate particles and the polymer coating resin to temperatures of ⁇ 300° F. ( ⁇ 149° C.) or more. In addition, in most cases this mixture must also be subjected to high intensity mixing. This is because these procedures are necessary not only to insure that each individual proppant substrate particle is provided with its own polymer resin coating but also to insure that the curable resin coated proppants ultimately produced are free-flowing in the sense that any clumping or agglomeration that may occur can be easily broken up with gentle agitation.
- these high heat and high intensity mixing steps can be avoided, because fully functioning resin coatings can be produced on proppant substrate particles by simple dispersion coating techniques which do not require these steps. This represents a significant advantage in terms of manufacturing these proppants, because the special equipment needed to carry out these high heat and high intensity mixing steps need not be used in connection with making these proppants.
- This feature of the invention finds particular advantage when conventional hydraulic fracturing sand (“frac sand”) is used to make the inventive resin coated proppants. This is because, in these instances, the inventive proppants can conveniently be produced in the same plant in which the frac sand is produced (the “sand plant”) simply be adding the mixing equipment needed to coat this frac sand with the aqueous polymer dispersions of this invention to the end of the frac sand production line.
- frac sand conventional hydraulic fracturing sand
- producing useful commercial grade sand products in a sand plant usually involves washing the raw sand to remove dirt and debris and then classifying the washed sand into predetermined sizes and/or grades.
- the raw sand is normally heated to elevated temperatures so that drying of the sand after washing and classifying can be accelerated by the latent heat in the sand.
- the cleaned and classified sand products produced by the sand plant are still warm after production has been completed.
- a particular advantage of this invention when conventional frac sand is used to make the inventive resin coated proppant is that the latent heat remaining in this frac sand product, after it is made, can be used to facilitate manufacture of this proppant rather than simply being wasted, as occurs in conventional practice.
- the amount of self-bonding addition copolymer coating that can be present in the inventive resin proppants, and essentially any amount can be used. So for example, polymer loadings (post drying) of as little as 0.1 wt % and as much as 20 wt. % on a dry weight basis, based on the weight of the proppant substrate particle, can be used. Typically, however, the amount of self-bonding addition copolymer coating will be about 0.3 to 5 wt. %, even more typically about 0.4 to 2 wt. %, or even 0.5 to 1.5 wt. %, on this basis.
- the consolidated proppant packs which are made from the inventive resin coated proppants when used in low temperature and low closure stress applications, exhibit superior conductivities even when these proppants are made with less polymer resin than conventional curable resin coated proppants available in the past.
- the curable polymer resins which are normally used to make conventional curable resin coated proppants are either novolacs or phenolic urethanes. Normally, about 1.5 wt. % or more of these polymers, based on the weight of the proppant substrate particle, are used to make these products.
- the inventive resin coated proppant exhibits better conductivities than otherwise identical curable resin coated proppants made with these novolac and/or phenolic urethanes.
- the amount of self-bonding addition copolymer coating that is present in the inventive resin coated proppants is desirably maintained at 0.3 to ⁇ 1.5 wt. %, more typically, 0.4 to 1.4 wt. % or even 0.5 to 1.3 wt. %.
- % 0.5 to 1.1 wt. %. and 0.5 to 0.8 wt. % are contemplated, as are polymer loadings of ⁇ 1.0 wt. %, ⁇ 0.8 wt. %, ⁇ 0.6 wt. %.
- the inventive resin coated proppants may be exposed to temperatures as high as 120° F. ( ⁇ 49° C.) and relative humidities as high as 80-90% during storage and shipment. As a result, they may undergo premature clumping and/or agglomeration, making them difficult or impossible to use.
- the outer surface of the proppant's polymer resin coating can be chemically modified such as by crosslinking or the like.
- the extent and/or degree of this chemical modification/crosslinking should be enough to prevent the resin coatings of contiguous proppants from bonding together that would otherwise occur during storage and shipment, but not so much as to prevent bonding once the proppant reaches its intended destination downhole.
- any chemical modifier which will prevent or retard additional bonding from occurring at the very surface of the proppant's addition copolymer resin coating can be used.
- Examples include phosphorous oxychloride, epichlorohydrin, epoxy and its derivatives, polymeric diisocyanate and their derivatives, polymeric carboxylic acids, anhydrides, aldehydes, borates and their derivatives, guar and its derivatives.
- these proppants when these proppants reach their ultimate destinations downhole, the elevated pressures encountered there are sufficient to degrade this protective shell, thereby releasing the bondable resin coatings underneath. As a result, contiguous proppant particles can bond to one another to form a strong, coherent proppant pack in a conventional manner. In a sense, therefore, these proppants can be considered to be “pressure-activated,” because it is the elevated pressures encountered downhole which cause these proppants to bond to one another.
- inventive curable resin coated proppants with a suitable partitioning agent, also known as “anti-caking” agents.
- suitable partitioning agent also known as “anti-caking” agents.
- suitable partitioning agent include sodium carbonate, sodium bicarbonate, sodium trimetaphosphate, calcium carbonate, calcium silicate, silica and its derivatives such as colloidal silica and fumed silica, talc, kaolin, bentonite, diatomaceous earth, microcrystalline cellulose, and attapulgate.
- the inventive resin coated proppants In addition to being able to self-bond at temperatures as low as 70° F. ( ⁇ 21° C.), the inventive resin coated proppants also exhibit a number of additional properties which make them ideally suited for use in the hydraulic fracturing of geological formations exhibiting low closure pressures (stresses).
- a “low closure pressure” will be understood to be a closure pressure of 6,000 psi or less.
- the crush strength of a resin coated proppant is a measure of the ability of individual grains of the curable resin coated proppants to resist proppant pack failure in response to a large applied stress. It is different from the UCS value (unconfined compressive strength) of the proppant, which is further described below, which is a measure of the strength of a proppant pack made from a curable resin coated proppant and, by implication, the strength of the polymer used to make this proppant.
- the crush strength of a curable resin coated proppant can be measured by the following analytical test: About 65 g of the proppant is poured into a test cell, after which a specified amount of pressure (e.g., 6000 psi to 12000 psi) is applied to the proppant via a piston. After releasing the pressure, the proppant sample is sieved. The amount of fines generated as a percentage of the total amount of proppant tested is measure of the crush strength of the proppant.
- a specified amount of pressure e.g., 6000 psi to 12000 psi
- the inventive resin coated proppants exhibit crush strengths which are essentially the same as that exhibited by the proppant substrate particles from which they are made. This shows that the polymer resin coatings of this invention do not adversely affect the crush strength of the product proppants ultimately obtained.
- UCS value is a measure of the ability of a proppant pack formed from a mass of the resin coated proppant to resist proppant pack failure when exposed to the temperatures and pressures likely to be encountered downhole. It is also an accurate measure of the ability of a proppant to resist proppant flowback, since most proppant flowback occurs when failure of a proppant pack occurs. It is also an accurate measure of the strength of the curable polymer resin that is used to make the proppant, once this polymer resin is cured. UCS value is not a measure of proppant crush strength, which as indicated above is measured by a different test.
- the UCS value of a proppant is a function of temperature in the sense that the ability of a proppant pack to resist proppant pack failure in response to an applied pressure depends on its temperature.
- the UCS values of a resin coated proppant can be determined by the following analytical test: This test involves two parts, creating a test specimen followed by testing of the specimen so made. To create the specimen, a quantity of the proppant (e.g., 85 g) is mixed with a 2% aqueous KCl solution for 5 minutes to simulate the naturally occurring water the proppant will likely see in use downhole. The proppant slurry is then poured into a cylindrical UCS cell assembly, one side of which has a screen to remove any excess liquid while the other side has a sliding piston.
- This test involves two parts, creating a test specimen followed by testing of the specimen so made. To create the specimen, a quantity of the proppant (e.g. 85 g) is mixed with a 2% aqueous KCl solution for 5 minutes to simulate the naturally occurring water the proppant will likely see in use downhole. The proppant slurry is then poured into a cylindrical UCS cell assembly, one side of which has a screen to remove any
- the cell assembly so formed is then maintained for a suitable period of time (e.g., 24 hours) at the predetermined temperature of the test (e.g., 150° F., ⁇ 66° C.) and predetermined pressure (e.g., 1000 psi, ⁇ 6,894,757 N/m 2 ) which simulate the temperature and pressure the proppant will see in its ultimate use location downhole.
- predetermined temperature of the test e.g., 150° F., ⁇ 66° C.
- predetermined pressure e.g., 1000 psi, ⁇ 6,894,757 N/m 2
- This causes any liquid remaining in the proppant mass to be removed through the screen and the individual proppant particles to consolidate as a result of particle-to-particle bonds that form as the resin coatings on each proppant particle cure.
- the result is that a specimen is formed in the shape of the UCS cylindrical cell, this specimen being a consolidated mass of proppant, i.e., a proppant pack
- the specimen so formed is then tested for its UCS value. This is done by placing the specimen in an automated press which measures the maximum axial compressive stress the specimen can withstand before failure of the proppant pack occurs. Note that, in this test, the specimen is unconfined in the sense that its cylindrical walls are free of any support. As a result, the value generated by this test, which is referred to as the unconfined compressive strength of the resin coated proppant, and which is normally given in psi or N/m 2 , is an accurate measure of the ability of the proppant pack so formed to resist degradation at the simulated conditions of the test.
- the inventive resin coated proppant normally exhibits UCS values at 70° F. ( ⁇ 21° C.) of at least 10 psi ( ⁇ 69,000 N/m 2 ). More typically, the inventive curable resin coated proppant exhibits UCS values at 70° F. ( ⁇ 21° C.) of at least 20 psi ( ⁇ 440,000 N/m 2 ), at least 30 psi ( ⁇ 207,000 N/m 2 ), or even at least 40 psi ( ⁇ 275,000 N/m 2 ).
- the inventive resin coated proppant normally exhibits UCS values of at least 20 psi ( ⁇ 140,000 N/m 2 ), more typically at least 40 psi ( ⁇ 275,000 N/m 2 ), at least 60 psi ( ⁇ 415,000 N/m 2 ), at least 80 psi ( ⁇ 550,000 N/m 2 ), at least 100 psi ( ⁇ 690,000 N/m 2 ), at least 120 psi ( ⁇ 830,000 N/m 2 ), or even at least 150 psi ( ⁇ 1,035,000 N/m 2 ).
- the conductivity of a resin coated proppant is a measure of the ability of a consolidated mass of the proppant, i.e., a proppant pack, to conduct fluid—oil, water, and gas—from a subterranean formation containing the proppant pack to a wellbore penetrating the formation. It is a function of both temperature and pressure.
- the conductivity of a resin coated proppant can be measured by the following analytical test: A quantity of the proppant to be tested is sandwiched between two sandstone plugs or cores in a conductivity test cell. The cell is then placed in a hydraulic press, whose platens/pistons are arranged to exert a compressive stress on the proppant acting through the two sandstone plugs/cores. Pressure transmitters are connected to the inlet and outlet of the cell to record the differential liquid pressure across the pack, i.e., the difference between the pressure of the test liquid flowing into and out of the pack. The cell is then heated to the temperature of the test, using heaters or heating liquid flowing through a metal jacket.
- the conductivity of the proppant is then measured at a series of different compressive stresses typically ranging from 2,000 psi (13.8 MPa) to as much as 14,000 psi (96.5 MPa) or more.
- the test starts by flowing a heated 2% KCl test solution through the proppant pack at an applied compressive stress of 50 psi (0.34 MPa).
- the applied compressive stress is then increased to 2,000 psi (13.8 MPa), and the flow rate of the test liquid through the pack as well as its pressure drop across the pack are record. This procedure is repeated a number of times at successively greater applied pressures, usually by increments of 2,000 psi (13.8 MPa), with a typical test lasting as long as 10 days or even longer.
- Proppant conductivity which is determined using Darcy's law and is given in millidarcy-feet or md-ft at the particular temperature of the test, is recorded at the different pressures tested.
- the inventive resin coated proppant exhibits conductivities which are at least as good as, and often better than, the conductivities exhibited by the proppant substrate particles from which this inventive proppant is made, at least at low closure pressures. This shows that the polymer resin coatings of this invention do not adversely affect the conductivity of the product proppants ultimately obtained.
- 1 kg samples of 20/40 frac sand were coated with a self-bonding polymer resin in an amount of either 1 wt. % or 2 wt. %, based on the proppants substrate particles being coated.
- Two different commercially available liquid polymer systems were used for this purpose, both of which were aqueous dispersions of copolymers of styrene and an acrylic acid ester. This was done by introducing the sand into a mixing device (Kitchen Aid mixer) followed by introducing the liquid polymer systems with mixing. In these examples, the sand was preheated to 160° F. ( ⁇ 71° C.), although this is unnecessary.
- Table 1 also shows that the crush strengths of the inventive resin coated proppants of Examples 1 to 4 are essentially the same as the crush strength of the raw sand control. This shows that the polymer resin coatings of this invention do not adversely affect the crush strength of the product proppants ultimately obtained.
- the inventive resin coated proppant of Example 1 as well as the uncoated frac sand control were was also tested for proppant conductivity at 150° F. ( ⁇ 66° C.).
- the proppants were subjected to successively increasing pressure levels from 2,000 psi to 10,000 psi, and the conductivities of the proppants measured immediately after each of these pressure levels was reached.
- the maximum pressure level used was 10,000 psi.
- Table 2 The results obtained are set forth in the following Table 2.
- the conductivity of the inventive resin coated proppant was greater than that of conventional frac sand at applied pressures up to 6,000 psi. This indicates that, when the inventive curable resin coated proppant is used in subterranean formations having relatively low closure stresses such as ⁇ 6,000 psi or less, the polymer resin coatings of these proppants do not decrease, but actually increase, the conductivities of these proppants.
- inventive resin coated proppants of Examples 1-6 were stored at room temperature for up to several months, after which they were tested for clumping/agglomeration. No substantial clumping/agglomeration was found.
- a number of different resin coated proppants were prepared using 20/40 grade conventional frac sand as the proppant substrate particles. In some cases, these proppants were made with the conventional curable polymer resins used to make conventional curable resin coated proppants, while in other instances these proppants were made in accordance this invention. All were tested for proppant conductivity at temperatures ranging from 125° F. ( ⁇ 52° C.) to 250° F. ( ⁇ 121° C.) at pressure levels ranging from 2,000 psi to 10,000 psi. Uncoated frac sand was also tested as a control.
- the data in this table also shows that at applied pressures up to 6,000 psi, and except for Comparative Example E in which the proppant was made with 1.5 wt. % of a conventional phenolic novolac resin, the inventive resin proppants exhibited conductivities at different temperatures which were at least as good as and in most instances better than that exhibited by uncoated raw sand as well as the conventional resin coated proppants, even though the amount of curable polymer resin used (0.5 wt. %) was substantially less than that used in the conventional resin coated proppants (0.75 wt. % and 1.5 wt. %).
- inventive resin coated proppants when used in subterranean formations having lower closure pressures and temperatures, can provide proppant conductivities significantly better than that provided by conventional curable resin coated proppants even though the amount of curable polymer resin used is considerably less.
- the conductivity of a proppant pack formed from one of the inventive resin coated proppants of Example 1 when exposed to a simulated closure pressure of 8000 psi (55.2 N/mm 2 ) pressure at 150° F. (65.6° C.) was periodically measured over the course of 250 hours.
- the same conductivity test was carried out on a proppant pack made from a conventional novolac resin coated proppant.
- inventive resin coated proppant exhibited conductivities almost as good as that exhibited by the conventional novolac resin coated proppant for the entire 250 hour duration of the test. This demonstrates that the inventive resin coated proppant performs essentially as good as its conventional counterpart, even though it is far easier and less expensive to make because less polymer resin is needed and further because high temperature/high intensity mixing techniques are unnecessary.
- the inventive resin coated proppants exhibit good UCS values (>10 psi) even at lower temperatures (70° F.), even though they are made with less curable polymer resin than the conventional products, at higher temperatures such as 200° F., the inventive resin coated proppants exhibit even better UCS values (>50 psi), again at 1,000 psi, no special equipment or procedures such as heating to high temperatures or high shear mixing are needed to make the inventive resin coated proppants since they can be made by simple coating techniques such as spay coating and the like at room temperature, the inventive curable resin coated proppants are storage stable, even at high ambient temperatures and humidities, when tested at 150° F.
- the resin coatings of the inventive proppants do not adversely affect, and indeed often improve, proppant conductivities when used in subterranean formations having low closure pressures of about 6,000 psi, the resin coatings of the inventive proppants do not adversely affect their crush strengths, and the inventive resin coated proppants do not interact negatively with other frac fluid components.
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Abstract
Description
TABLE 1 |
UCS and Crush Strength of Inventive Proppants |
Resin |
LOI, | Silica | UCS, psi | Crush Strength, psi |
Ex | Type | wt. | wt. % | 70° F. | 50° F. | 6K | 7K | 8K | 9K | |
A | none | 7.1 | 10.8 | ||||||
1 | α | 1 | 0.05 | 40 | 9 | 11.5 | |||
2 | β | 1 | 0.05 | 69 | 8.8 | 12.2 | |||
3 | α | 2 | 0.10 | 180 | 6.1 | 8.1 | 10.6 | ||
4 | β | 2 | 0.10 | 109 | 9.4 | 11.4 | |||
5 | α | 1 | 0.03 | 27 | |||||
6 | β | 1 | 0.03 | 25 | |||||
TABLE 2 |
Conductivities of Proppant of Example 1 and Conventional |
Frac Sand @ 150° F. |
Conductivity, mD/ft |
Applied Pressure, psi | Example 1 | Frac Sand Control |
2,000 | 4521 | 3707 |
4,000 | 3499 | 3010 |
6,000 | 2100 | 2094 |
8,000 | 1004 | 1382 |
10,000 | 448 | 772 |
TABLE 3 |
Conductivities of Various Proppants and Conventional Frac Sand at Different Temperatures |
Conductivities in mD/ft at different | |||
Polymer Resin | press, psi |
Ex | Type | Wt. % | Temp, ° F. | 2K | 4K | 6K | 8K | 10K |
B | Raw Sand | 150 | 2780 | 2179 | 1435 | 981 | 669 | |
7 | Styrene/acrylate copoly-α | 0.5 | 150 | 3561 | 2414 | 1391 | 836 | 461 |
8 | Styrene/acrylate copoly-β | 0.5 | 150 | 3379 | 2343 | 1358 | 785 | 432 |
C | Raw Sand | 250 | 2654 | 2082 | 1305 | 834 | 494 | |
D | Phenolic Novolac | 0.75 | 250 | 2775 | 2065 | 1165 | 554 | 288 |
E | Phenolic Novolac | 1.5 | 250 | 2580 | 2280 | 1682 | 1136 | 694 |
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MX2014012609A (en) * | 2012-04-19 | 2015-01-19 | Self Suspending Proppant Llc | Self-suspending proppants for hydraulic fracturing. |
MX2015012963A (en) * | 2013-03-15 | 2015-12-01 | Basf Se | A proppant. |
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Also Published As
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WO2018175142A9 (en) | 2018-12-13 |
WO2018175142A1 (en) | 2018-09-27 |
DK181044B1 (en) | 2022-10-18 |
AR111335A1 (en) | 2019-07-03 |
CN110520501A (en) | 2019-11-29 |
CN110520501B (en) | 2022-10-25 |
CA3055302A1 (en) | 2018-09-27 |
NO20191161A1 (en) | 2019-09-26 |
DK201970570A1 (en) | 2019-09-25 |
US20180265772A1 (en) | 2018-09-20 |
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